9-1 prentice hall ©2008 pearson education, inc. upper saddle river, nj 07458 forensic science an...
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9-3 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The Bases Four types of bases in DNA structure: adenine (A) bonds w/ thymine (T). Guanine (G) bonds w/ cytosine (C)TRANSCRIPT
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Chapter 9
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
DNA (deoxyribonucleic acid)DNA codes for proteinsEveryone’s DNA is unique w/ exception of
identical twinsDNA made by linking a series of repeating
units called nucleotides.
The sugar/phosphate make up backbone of DNA “ladder”
The nitrogen bases make up the “rungs” of the ladder
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
The BasesFour types of bases in DNA structure: adenine (A) bonds w/ thymine (T).Guanine (G) bonds w/ cytosine (C)
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
DNA TypingTandem repeats seem to act as filler or
spacers between the coding regions of DNA.
all humans have the same type of repeats, but there is tremendous variation in the number of repeats each of us have.
Two main procedures: STR analysis and RFLP
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
RFLPLength differences associated with
relatively long repeating DNA strands are called restriction fragment length polymorphisms (RFLP)
Different lengths result from cutting DNA molecule w/ restriction enzymes
-Typically, a core sequence consists of 15 to 35 bases in length and repeats itself up to a 1000x
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
RFLPAdvantages
RFLP’s completely unique from person to person(except id.twins)
Can be used to identify genetic diseases
Disadvantages
Requires a lot of DNACan’t be used with
PCR to copy more DNA
Degrades more quickly
Can’t store results in database
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
RFLP Data for sickle cell
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Paternity Test
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Paternity test
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
PCRPolymerase chain reaction (PCR) is a technique
for replicating small quantities of DNA or broken pieces of DNA found at a crime scene
This means that sample size is no longer a limitation in characterizing DNA recovered at a crime scene.
3 STAGES: denaturing, annealing, synthesizing
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
3 stages PCR:1) Denature: DNA strands separated2) Annealing: primer attaches to DNA site
being copied3) Synthesizing: piece of DNA is copied/total
DNA is doubled with each cycle
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Short Tandem Repeatsshort tandem repeat (STR) analysis, most
widely used DNA profiling procedure. STRs are locations on the chromosome
that contain short sequences that repeat themselves within the DNA molecule.
STRs repeating sequences of 3 to 7 bases in length, entire strand of an STR is also very short, less than 450 bases in length.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
STR AdvantagesSTRs less susceptible to degradation and
may often be recovered from bodies or stains that have been subjected to extreme decomposition.
STRs are ideal candidates for multiplication by PCR
STR is numerical data and can be kept in a database
With STR, requires 100x less DNA than normally required for RFLP analysis.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
STR example
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Standardizing STR TestingU.S. crime laboratories have standardized 13
STRs for entry into a national database (CODIS).
A high degree of discrimination can be attained by multiplexing -analyzing a combination of STRs and determining the product of their frequencies.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
STR Analysishttp://www.dnalc.org/view/15983-Today-s-DNA-profile.html
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Paternity Test
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Determine missing person Mom Daughte
rSon Dad
D3S1358
12, 12 12, 14 16, 12
vWA 11, 14 11, 11 11, 14
FGA 13, 17 13, 15 17, 15
TH01 9,9 9, 10 11, 9
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Determine Paternity Mom Son Dad? D3S1358 14, 14 14, 15 15, 12
vWA 11, 7 7, 13 13, 8FGA 6, 8 6,6 6, 9
AMEL 12,14 12, 11 12, 15
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Mitochondrial DNAAnother type of DNA used for
identification is mitochondrial DNA. Mitochondria have own DNAOne cell has several mitochondria, a lot of
mitochondrial DNA present in 1 cell
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Mitochondrial DNA TestingMitochondrial DNA typing best for
samples, such as hair, for which STR analysis may not be possible.
Forensic analysis of mDNA is more rigorous, time consuming, and costly when compared to nuclear DNA analysis.
all individuals same maternal lineage will be indistinguishable by mDNA analysis.
Two regions of mDNA have been found to be highly variable and a procedure known as sequencing is used to determine the order of base pairs.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
CODISCODIS (Combined DNA Index System) is a
computer software program developed by the FBI that maintains local, state, and national databases
DNA profiles from convicted criminals, sex offenders, unsolved crime scene evidence, and profiles of missing persons.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Packaging Biological EvidenceWearing disposable latex gloves while
handling the evidence is required.
Clothing from victim and suspect must be collected.
The packaging of biological evidence in plastic or airtight containers must be avoided because the accumulation of residual moisture could contribute to the growth of DNA-destroying bacteria and fungi.
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PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458
FORENSIC SCIENCE An IntroductionBy Richard Saferstein
Packaging Biological EvidenceEach article should be dried and packaged separately
in a paper bag or in a well-ventilated box.Dried blood is removed by using a sterile cotton swab
moistened with distilled water , air dried before being placed in a swab box, then a paper or manila envelope.
All biological evidence (blood samples) should be refrigerated or stored in a cool location
Standard/reference DNA specimens must also be collected, such as blood or the buccal swab (swabbing the mouth and cheek).